Fluid flow machines such as axial or transversal compressors are the most efficient and compact devices for compressing fluid or generating a fluid flow with high volumetric throughput. Similarly fluid turbines are also very efficient power plants for converting energy of flowing fluid to drive a rotary power shaft. However, they are also the most expensive and intricate equipment to design, build and test. This limits their application to very special instances such as aircraft jet engines, industrial gas compressors, pipeline transports and others. Design of existing fluid flow machines are such that they cannot be built at low enough cost to be used in many environmentally friendly applications. One such desirable application is in the area of refrigeration requiring vacuum vapour compressors with large volumetric throughput when using water as a refrigerant.
Conventional axial fluid flow machines such as air compressors use multiple stages of rotor and stator disc pairs arranged alternately in a coaxial configuration inside a shroud. Each rotor/stator disc comprises multiple blades mounted on a center hub. In each stage the fluid entering the rotor is compressed and moved along towards the stator disc where further compression may take place along with redirecting of the fluid for optimum entry into the next downstream rotor.
In multi-stage machines, the rotors driven by a power source compress as well as impart high velocity to the contact fluid that velocity is then converted into additional pressure by the stators to progressively raise the pressure from stage to stage. The back flow is minimized by providing very tight clearances and labyrinth seals between the shroud and the rotors and between rotors shaft and stators. In the case of turbine power plants, the contact fluid is imparted high pressure by mechanisms such as combustion, ignition, or some other energy source. The contact fluid under pressure drives a rotor or rotors which is used as a source of power, such as electrical generators, engines, etc.
The blades are profiled and dimensioned to run at particular Mach number and Reynolds number conditions for optimum performance. With the evolution of the technology, it is recognized that the two important factors which determined the improvement in performance are blade aspect ratio and tip to shroud clearance. As both are reduced, considerable improvement in stage pressure ratio is realized.
Blade design is a complex art. Each individual blade acts like a cantilever wing which can flex in torsion as well as in bending. Deviation from the ideal flow direction can cause aerodynamic stall of the blade leading, possibly, to what is commonly known as surge condition. This latter phenomenon can cause blade vibration which may result in the structural failure of a blade totally destroying the entire compressor.
In U.S. Pat. No. 4,029,431 Jun. 14, 1977, Bachl describes a fluid flow machine which includes a combination of rotating and non-rotating wheels. Each wheel has fluid flow channels which are shaped and located in such a way that upon rotation of wheels, desired fluid flows are created. The shapes and locations of channels are carefully designed to direct the fluid flow medium to have a transverse and an axial component relative to the axis of rotation of the rotating wheels. It should however be recognized that such shapes and locations of channels require complicated design and manufacturing procedures.
The current invention completely dispenses with the individual blade concept in favour of a disc with open narrow bubbles, acting as scoops, formed directly into the disc. The disc is housed in a shroud and is rotatable about an axis which is substantially coaxial with the shroud. The shroud is cylindrical in shape in some embodiments but it could be of any symmetrical shape such as frustum, stepped frustum etc. The bubbles are arranged to intercept the fluid and pass it through the openings as they rotate integrally with the disc.